Artificial joints for lower extremities can be used in orthoses or prostheses. Orthoses are needed to assist or maintain the function of the still present lower extremity. For this purpose, the orthoses are secured on the still present extremity. In the case of a knee orthosis, splints are placed on the upper leg and on the lower leg and are connected to each other via an orthotic knee joint. In the case of an ankle orthosis, the foot is fixed to a foot part, which is connected to a lower leg splint via an orthotic ankle joint. The same applies for a hip joint orthosis. In principle, it is also possible to provide an orthosis with more than two joints.
Missing limbs are replaced by prostheses. In the case of prosthetic knee joints, the missing knee joint is replaced by a prosthetic knee joint whose upper part is secured to an upper leg stump by an upper leg socket. The lower part is secured pivotably on the upper part of the prosthetic knee joint. A lower leg tube and a prosthetic foot, if appropriate with a prosthetic ankle joint, are arranged on the lower part. It is likewise possible, in cases of exarticulation of the hip, to replace the missing hip joint with a corresponding exoprosthesis.
Patients with limited motoric abilities sometimes need assistance when performing movements that require force. These in particular include standing up or sitting down, since a considerable part of the body weight has to be moved vertically during these actions. When standing up, the body weight has to be lifted; when sitting down, it has to be lowered in a controlled manner. In the case of prosthesis users, the intact leg generally has to assume the entire work, optionally with the assistance of the arms. The situation is comparable in the case of orthosis users who have only limited motoric abilities in the treated leg.